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So I posted a little on this old thread and Ron D gave me some good ideas https://www.ranger-forums.com/4-0l-o...around-167666/
I have searched every available thread on the subject and condensed it into a checklist I made to test every possible item folks have suggested.
Basically the gauge gets to just past the halfway point after warm up and then apparently the thermostat opens and it drops down to about 1/3. Then it rises and falls seemingly indifferent to whether I am on the highway or around town. This goes on no matter the duration of the drive or type of driving, just a continuous cycle. After maybe a long highway drive the fluctuations get smaller.
Changed temperature sensors (1 and 2 wire), heater core, radiator cap, fan clutch, blocked radiator in front. Tried multiple thermostats, STANT, Motorad, currently a Motorcraft RT1139. Checked voltage (steady, no correlation to fluctuation), checked heat from panel vent (fluctuates with gauge 5 degrees or more) 140-145F or 145-150F depending on day. Checked panel gauge key on grounded and not grounded and it's fine. I still have a substantial difference in top and bottom hose temps using a contact Fluke meter and IR Fluke meter (30 degrees or more). Fan shroud is in place.
General maintenance new harness, plugs, cap, rotor, clean MAF, clean sensor at air filter, clean K&N airfilter, new timing chain cover gasket and timing chain, new water pump at about 195K, new O2 sensors on the exhaust system. Combed the radiator fins and blew out a bunch of bugs.
I'm thinking the new fan clutch is just locked all the time?
I re-visited the fan clutch I replaced, noted that when cold before first start it had some resistance to turning. After running for a minute or more I shut the engine off and it still has resistance. After running for 20 minutes it still has resistance. Never does it really spin freely, or what I think spinning freely means. The gauge does hit the halfway mark at about 10-15 minutes of running which I think is about right.
I noticed that my mileage has dropped a few miles per gallon (not that it was super to start with, 20mpg city to 17 mpg city, I drive like a little old lady I guess).
I had read in the threads that Hayden is making the Motorcraft brand fan clutches and one person noted an issue with their 'Motorcraft' clutch. Is there a brand I need to look at or is there some mysterious fan clutch information I have missed?
I will check for codes (again) and pull the belt to check if any accessories are dragging (alternator, power steering pump, AC pump, water pump, idle pulley).
Looking forward to Ron D comments!
Dave/Vancouver WA
93 Ranger 4wd 3.0 V6 215K miles, head gaskets at 210K
interesting im going to check my fan resistance before startup and when motor is warmed up. temp gauge is 1/2 way. also what is the outside temperature ?
45-60F these days. I tried blocking over a third of the radiator with roof flashing wired in to no effect, just to see. This phenomenon was happening last summer also when outside temps were warmer.
ok I just checked mine. theres still some resistance when motor is warmed up. the difference between cold and warm motor? some difference. I did have a bad new thermostat. new doesnt mean that it work. they are not tested.
Cold engine
Remove rad cap, see if its coolant level is at the very top, should be NO AIR at all in the top of radiator, you have a self purging system
If there is air
Remove either heater hose from the firewall
Top up radiator until coolant is coming out the core and hose, then put it back on, all air is now purged from engine side of thermostat, this is simply the easiest way to refill any engine's cooling system
Remove the over flow hose from radiator, blow thru it, air should bubble up inside the Overflow tank, this is the self purge hose, needs to be air tight and overflow tank needs to be clean at the bottom, so any air from radiator can come in and then bubble up to the top, and as engine cools down COOLANT is sucked back in replacing any air that came out, self purge
Radiator cap has 2 valves
The larger valve that holds pressure in the system as coolant warms up and expands in volume, usually 14psi
At 15psi the valve is pushed up and warm coolant flows over to the bottom of the overflow tank, along with any air that happened to collect at the top of the radiator
When system cools down the coolant shrinks in volume and pressure goes down, if any coolant was sent over to the overflow tank then pressure in the system will go to -1psi, this will suck open the smaller valve in the center of the radiator cap and coolant from the overflow tank will be pulled back in, self purge
(if you ever see collapsing upper rad hose on cool down that means this smaller valve is bad or the overflow hose/tank is blocked)
So at any time engine is cold when you open the rad cap there should be NO AIR AT ALL at the top, if there is then there is a problem somewhere
Air is much easier to move that coolant, so even a small coolant leak will allow air to be sucked back in as engine cools down instead of coolant from the tank
Random temp changes can be air, but there are other reasons as well, but take air off the table first as that's easy to test for with above info and a few drive cycles, i.e. full warm up and cool down
Can be a bad thermostat, not staying open and steady, opening and closing randomly
Fan clutch maybe but they tend to fail closed so too much cooling and loud, called "fail safe" to prevent over heating, thermostats should also fail opened, for the same reason, but either can fail in different ways
Blockage in a heater hose or core, or heater by-pass valve if it has one
so does that mean that the temp gauge was working normal normal for a while?
Yup, before timing chain cover gasket and head gasket replacement.
Remove rad cap, see if its coolant level is at the very top, should be NO AIR at all in the top of radiator, you have a self purging system
We're good. You taught me the trick about the heater core hoses to remove at firewall when changing thermostats or bleeding air. Works like a charm. Cold engine the coolant is up to the cap. No gurgles in the heater lines, I also purge air when mucking with the system while on an incline.
Remove the over flow hose from radiator, blow thru it, air should bubble up inside the Overflow tank, this is the self purge hose, needs to be air tight and overflow tank needs to be clean at the bottom
Yup, clear and clean. Wish I could remove the tank and REALLY clean it out but it's kind of a can of worms....
Blockage in a heater hose or core, or heater by-pass valve if it has one
New heater core, hoses new a few years ago but clear, heater works great. I think on the '93 it's just a constant flow thru the core, don't know about a by-pass.
Can be a bad thermostat, not staying open and steady, opening and closing randomly
This is probably the 5th thermostat I tried, finally found a Motorcraft RT1139, does the same thing.
I'll check the tightness of the overflow tank and hose. The coolant level is rock solid when cold which relieves me greatly after the head gasket work.
So I found this tidbit below in the posts and was wondering what the original 93's came with, either standard, heavy, or severe duty fan clutches on the 3.0 engines. I researched the fan clutch the counter fellow sold me I currently have and it turns out it's a severe duty clutch which I probably don't really need here in the Pacific Northwest. Is it feasible that the fan clutch/radiator/thermostat are just arguing with each other and not settling down? I have access to a 'standard' duty fan clutch but would like to know if anyone has any other ideas.
Hayden is the brand you want. Normally I'd say go with a "sever duty" clutch, but from what I know about geogrophy (not much) I don't think your truck sees much 100F+ temps..
If you indeed don't see those extreme temps I'd go with a "Heavy Duty" fan clutch from hayden at the most.
The different duty clutches spin at differenct % of the shaft speed.. The higher the percentage the more air it pulls which means the more mileage you can loose.
The fans engage at 170F temp (thats 170F air temp at the clutch).
Here is the info about the clutches.. I got this from a Hayden catalog.
Standard duty thermal clutch..
60%-70% when engaged (hot)
20%-30% when disengaged
Heavy Duty
70%-90% when engaged
25%-35% when disengaged
Severe Duty
80%-90% when engaged
20%-30% when disengaged.
The fan is really only used when driving slow or stopped
Driving over say 30MPH forces more air thru the grill and radiator than any fan could pull thru
So in general fan clutch issues show up when stopped and temp starts to go up on the gauge
Fan clutch is activated by radiator heat, as the center of the radiator warms up the heat is transferred to a bi-metal coil or bar on the front of the clutch, as the spring expands it closes off valves in the clutch area which causes the fan to pull more air, to spin closer to water pump RPMs(i.e. the % above)
Simple test for fan clutch
In the morning before starting the cold engine, open the hood and spin the fan, should be hard to spin
It should be cold Locked as the cold oil inside it is thicker, so mimics engaged/locked
Leave hood open
Start the engine, should HEAR the cold locked fan pulling in lots of air, but that should go away within 5-10 seconds, and noise drops away
Shut off engine
Spin fan again, should spin easily, unlocked
After going about your day driving and when you get home with warmed up engine, shut it off
Open the hood and spin the fan, should be partially locked or locked depending on radiator/engine temp
Yes, I've tried the 'spin easily' testing and it never does really spin easily in any scenario i.e. give it a push and the blades will spin on their own for maybe a revolution or so.
The fan does make plenty of noise on start up, this must be the 'cold lock'. It takes maybe several minutes of driving before it gets a little quieter.
I can't correlate a temp rise when I'm at a stop light. I do get a temp rise when I'm climbing a hill for several minutes but it is barely past the halfway mark on the gauge.
Can this 'severe duty' fan clutch be the a reasonable cause of lower gas mileage as stated in the quote I posted? Even though it might not be contributing to more cooling it could certainly be causing a lot more drag than necessary.
A 'standard duty' fan clutch from Hayden is $42 here locally and I'm not averse to trying it.
O2 sensors effect MPG the most, 12 years or 100k miles and they are done, MPG slowly starts to drop after that, no codes until they complete die
They are the Only sensors that wear out
here's a thought. like Ron said you dont need a fan driving at speeds over 30mph. so its likely not the fan. if you pulled the thermostat the temp would stay cold for quite a time and slowly warm up. you would need to drive it for some time. if the gauge still fluctuates its not the fan or thermostat. is it the gauge or sender or obstruction in the line? I guess you could bypass the heater and try it? does the fluid fluctuate in the catchment bottle? maybe run it with the cap off? see what happens ?
O2 sensors effect MPG the most, 12 years or 100k miles and they are done, MPG slowly starts to drop after that, no codes until they complete die
They are the Only sensors that wear out
Yup, new Bosch 02 sensors about 2 years ago
if you pulled the thermostat....
That is an interesting idea, I would have to work up some courage to try it as it's outside my comfort zone.
Does anyone know what the OEM fan clutch Motorcraft number is for a 93 Ranger 3.0 and whether it's a 'standard' or 'heavy duty'? Just looking at it from the mileage drop perspective for the moment. I know one of the members here bought a 'Motorcraft' fan clutch and it had 'Hayden' stamped on it. My searches show a lot of discontinued numbers.
I do have the OEM A/C unit in it if that makes a difference.
You need a restriction ring in place of the thermostat or engine will overheat with no thermostat
Take an old thermostat and remove the valve part if it, install that ring/plate
The coolant flow thru the engine is balanced by the sizes of the openings, if upper rad hose gets all the flow with no restrictions then there is less flow in other areas which then overheat
Well, finally figured it out. Found on an old thread on another Ford site that the fellow had the same problem with thumping and eratic temperature gauge fluctuations. After all the gyrations I went thru I tried his trick and it worked perfectly. My gauge is steady, no thumping, just like the old days. Basically he couldn't find that by-pass kit that Ford put together years ago so he thought about it and did a by-pass on the heater core hoses. Even with a new heater core apparently there was enough resistance to cause restriction to flow thru the heads. I did his by-pass trick and it worked. I had a new heater core, new hoses, etc. see above posts. What a simple solution.
The theory of steam forming in hot spots in the head may be valid, but increasing the flow of coolant, even just a little bit more, solved the problem. I still get plenty of heat in the cab also. The by-pass line is 3/8" I.D. whereas the main core hoses are 5/8" I.D.
